1. Technical Field
The present invention relates to ink jet printers and control methods therefor and, more particularly, an ink jet printer using an ink storage member that contains an absorber for absorbing and retaining an ink, and a control method therefor.
2. Related Art
An ink jet printer which belongs to a kind of ink jet printer is an apparatus that includes a permanent head and causes liquids of various kinds to be ejected (discharged) from the permanent head. This ink jet printer is a non-impact printing apparatus that forms characters on paper by ejecting particles or droplets of inks onto the paper (JIS X0012-1990). This ink jet printer is one of various forms of dot printers, this dot printer being a printer that performs printing of characters and/or images, each of the characters and images being represented by a plurality of dots (JIS X0012-1990), and the ink jet printer performs printing of such characters and/or images, each of the characters and images being represented by a plurality of dots, by forming the dots through a method of ejecting particles or droplets of inks. Further, the permanent head is a portion that includes mechanical and electric portions inside a printer body and that successively or intermittently generates liquid droplets of inks (JIS Z8123-1: 2013), and hereinafter, this permanent head will be referred to as an “ink jet head”. This ink jet printer has been used as an image recording apparatus, and besides, it has been applied to various manufacturing apparatuses in the form in which its characteristic of enabling each liquid droplet of a very small volume to be landed at a corresponding predetermined position with accuracy is exploited.
Such an ink jet printer is configured such that, for example, an ink storage member is attached to an ink jet head so as to be replaceable, and an ink stored in the ink storage member is flown into a flow path provided in the ink jet head. In addition, the ink storage member is also called, for example, an ink cartridge or an ink tank. There are various types for such an ink storage member, and among them, there is a foam type ink storage member that contains therein an absorber for absorbing and retaining an ink (refer to, for example, JP-A-2000-127431). In addition, the absorber is also called a porous material or foam.
In such a foam type ink storage member, a gradient arises in a concentration distribution of solid ingredients (including a pigment, a dispersing agent, and a resin material) of an ink retained in the absorber (in other words, concentration unevenness arises in the ink retained in the absorber) due to a difference between a specific gravity of the solid ingredients and a specific gravity of a solvent therefor, thereby also causing a gradient to arise in a viscosity distribution of the ink. More specifically, there is a tendency in that, in the absorber contained in an ink storage member being placed in a still state, the lower a position in a gravity direction becomes, the higher a concentration and a viscosity of the ink become; while the higher a position in a gravity direction becomes, the lower a concentration and a viscosity of the ink become. In the case of an ink storage member of a type in which the absorber is not used, it is possible to uniformize the concentration of the ink retained in the ink storage member to a certain degree by allowing a user to agitate the ink by means of, for example, shaking of the ink storage member, but in the case of an ink storage member of a foam type, it is difficult to eliminate variations in the concentration and the viscosity of the ink merely by means of the shaking of the ink storage member.
In general, the ink storage members are distributed in markets in a posture in which a connector portion thereof to be connected to an ink jet head (that is, a connection portion thereof from which the ink contained therein is flown out toward the ink jet head) is located at an approximately lower position in a vertical direction. Thus, a viscosity of an ink initially flown out from an ink storage member having been newly attached to the ink jet printer tends to be high. Thereafter, with consumption of an ink inside the ink storage member by ejection operations of the ink jet head, the concentration of the ink is gradually made uniform. The ink initially flown out from the newly attached ink storage member, however, has a larger flow-path resistance, compared with a desired ink (that is, an ink in a state in which its concentration and viscosity has been made stable to a certain degree after a certain period of consumption of the ink). Thus, when the ink initially flown out from the newly attached ink storage member is ejected under the same condition as that for the desired ink, as a result, a lack of an amount of an ink to be fed to a nozzle arises, thereby sometimes causing a phenomenon in which a meniscus is not correctly formed inside the nozzle. Further, this phenomenon is likely to cause a discharge failure, that is, a failure in that any ink is not ejected through the nozzle, or a failure in that, even though an ink is ejected through the nozzle, a direction of the ejected ink is deflected from a predetermined target direction.